Ground penetrating radar

• US 20030090406A1
• Filed: 10/17/2002
• Published: 05/15/2003
• Est. Priority Date: 02/29/2000
• Status: Active Grant

• Current Assignee: GroundProbe Pty Ltd. (Orica Limited)
• Original Assignee: GroundProbe Pty Ltd. (Orica Limited)
• Inventors: Noon, David, Cherniakov, Mikhail, Stickley, Glen Francis, Leat, Christhoper John, Longstaff, Denis
• Granted Patent: US 6,664,914 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: H01Q 9/28 Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines waveguide horns or mouths H01Q13/00; slot antennas H01Q13/00

Abstract

A ground penetrating radar comprises a signal generator, a return signal processor, gating means and antenna. The signal generator is a dual frequency synthesiser that generates a stepped frequency master signal and a tracking signal offset by an intermediate frequency. The return signal processor is a dual channel quadrature receiver that mixes down a return signal and a sample of the master signal to intermediate frequency using the tracking signal. The signal generator is pulsed by the gating means and the return signal is gated at the same frequency. Hollow pyramidal antennas are also described that have an ultrawide band bowtie structure with antenna electronics located within one antenna element. A method of operating the radar is also described.

Claims

1. A ground penetrating radar for detecting objects comprising:

signal generation means for

(i) generating and transmitting a stepped frequency master signal and

(ii) generating a tracking signal offset in frequency from the master signal by an intermediate frequency;

return signal processing means for

(i) receiving a return signal reflected from the ground region and

(ii) processing the return signal using the tracking signal and the master signal to determine amplitude values and phase values indicative of target matter;

gating means for

(i) pulsing the master signal and

(ii) gating the return signal; and

antenna means for

(i) coupling the master signal into the ground and

(ii) coupling a reflected signal from the ground.

2. The ground penetrating radar of claim 1 wherein the signal generation means is suitable a dual frequency synthesiser that generates stepped frequencies in the range between DC and GHz with kHz resolution.

3. The ground penetrating radar of claim 1 wherein the signal generation means generates clock signals for synchronisation of operation of the return signal processing means and gating means.

4. The ground penetrating radar of claim 1 wherein the return signal processing means includes a digital quadrature receiver and digital signal processing means.

5. The ground penetrating radar of claim 4 wherein the quadrature receiver is a dual channel receiver that mixes down a sample of the master signal and the return signal to the intermediate frequency using the tracking signal.

6. The ground penetrating radar of claim 4 wherein the quadrature receiver incorporates mixer means, bandpass filter means, analog to digital conversion means and digital down-conversion means.

7. The ground penetrating radar of claim 4 wherein the digital signal processing means is suitably one or more processor means programmed with suitable signal processing algorithms.

8. The ground penetrating radar of claim 1 wherein the antenna means are hollow elements.

9. The ground penetrating radar of claim 1 wherein the hollow elements are hollow pyramids aligned to have pairs of pyramids with adjacent apexes with a signal feed applied between the adjacent apexes.

21. A method of generating a radar signal for a ground penetrating radar of the type described in claim 1 including the steps of:

generating multiple narrower-band signals;

stepping said multiple narrower-band signals in frequency across an ultra-wide bandwidth;

generating a tracking signal for each narrower-band signal that is offset in frequency by an intermediate frequency from a centre frequency of said narrower-band signals; and

gating said multiple narrower-band signals.

22. The method of claim 21 wherein said narrower-band signals are stepped successively in frequency.

23. The method of claim 21 wherein said narrower-band signals are hopped non-successively in frequency.

24. The method of claim 21 wherein the duration of said narrower-band signals is variable.

25. The method of claim 21 wherein stepping said narrower-band signals involves a variable step or hop.

26. The method of claim 21 wherein the narrower-band signals are continuous sinusoidal waves.

27. The method of claim 21 wherein the narrower-band signals are noise signals.

28. The method of claim 21 wherein the narrower-band signals are the sum of many continuous sinusoidal waves of discrete frequencies.

10. An antenna means for a ground penetrating radar comprising:

a pair of hollow antenna elements, each antenna element having at least an apex, said hollow antenna elements being arranged such that said apexes are adjacent but not abutting;

electronics housed in one of said pair of hollow antenna elements; and

a coaxial connection between the apexes of said hollow antenna elements.

11. The antenna means of claim 10 wherein each said hollow antenna element has at least one triangular face and a triangular face from a first of said pair of hollow antenna elements is aligned in a common plane with a triangular face from a second of said pair of hollow antenna elements.

12. The antenna means of claim 11 wherein the hollow antenna elements are pyramidal.

13. The antenna means of claim 10 wherein each hollow antenna element of said pair of hollow antenna elements is a rectangular-based pyramid.

14. The antenna means of claim 10 further comprising a non radio frequency wave guiding connection to said electronics.

15. The antenna means of claim 10 wherein each hollow antenna element of said pair of hollow antenna elements comprises a pyramidal portion and an extension portion, said extension portion being an extension of a base of the pyramidal portion.

16. The antenna means of claim 10 further comprising shielding means surrounding said hollow antenna elements on all sides except a radar transmission or reception side.

17. The antenna means of claim 16 wherein a height of the shielding means is equal to a height of the base of the hollow antenna elements and a length of the shielding means is equal to a length of the pair of hollow antenna elements.

18. The antenna means of claim 16 wherein each said hollow antenna element is open at a base opposite said apex.

19. The antenna means of claim 16 further comprising dielectric material in spaces between said shielding means and said hollow antenna elements.

20. The antenna means of claim 16 further comprising a dielectric window across the said transmission or reception side.

29. A method of detecting objects with a ground penetrating radar including the steps of:

generating a stepped frequency radar signal;

pulsing said stepped frequency radar signal at a gating frequency;

transmitting the pulsed, stepped frequency radar signal into a region;

receiving reflected radar signals from said buried object in said region;

gating said received signals at said gating frequency;

down-converting said gated received signals to an intermediate frequency by mixing with a tracking signal;

digitally down converting said intermediate frequency to baseband; and

analysing a resulting radar image to detect said objects.

30. The method of claim 29 wherein said step of gating said received signals includes applying an inner gate and an outer gate to said received signals.